Dario IT Solutions Blog

One of the best new features in 2008 clusters is the ability to have cluster nodes on different subnets.

This is done by introducing a new OR dependency option for resources. In 2008 clusters, you have two options when making a resource depend on more than one resource:

• AND – Both the resource in this line and one or more previously listed resources must be online before the dependent resource is brought online.
• OR – Either the resource listed in this line or another previously listed resource must be online before the dependent resource is brought online.

So with the OR dependency, you can set up your cluster Network Name resources using an IP address from multiple subnets.

When you create your cluster or an application group, you are prompted to provide an IP address for each subnet. For example:

Here, you would enter a valid IP address for each subnet. Once this is complete, the cluster will automatically setup these dependencies properly for you and only one of the IP resources will be online at a time as the other IP address is not valid for the active node.

Some important notes:

1. Failover Cluster Quorum Type
   1. Node and File Share Majority is the best quorum type for geo-clusters
   2. Especialy if your file share will be located on a third site (that has no cluster members in it)
   3. Just remember, File Share Witness:
      1. Need to be on a File Server in the same forest
      2. No need to use shared storage – just a normal share
      3. Can’t be a node in the cluster
      4. Used as a decision making point for majority
      5. Can be used for multiple clusters (each cluster has a different share)
2. DNS Considerations
   1. Upon failover to the other node, DNS records will be updated to point to the new IP address. While this is occurring, clients may not be able to connect to the cluster workload even though it is online
   2. Use “RegisterAllProvidersIP” to control which dependent IP address are registered
   3. Use “HostRecordTTL” to control time-to-live on cluster network name resources (For ex. – 5 minutes is recommended for Exchange 2007)

Related posts:

1. Hyper-V Deployment – Notes from the field
2. Hyper-V Failover Clustering Using Normal Shares
3. Windows 2008 R2 NLB & Failover Clustering
4. Windows Server 2008 Hyper-V Storage
5. Clustering Webcasts